I was sitting around munching some code, and needed to filter a list I had:

List<Whatever> list = // get list

outputList = list.FindAll(delegate(Whatever item)
{
   if (// blah blah)
   {
      return true;
   }
   else
   {
   return false;
   }
}
);

(Ignore the greyed-out text for now).

When compiling, I got a strange error message:
"cannot convert from 'anonymous method' to 'System.Predicate<Whatever>'".

This put me off for a few minutes while I tried checking code samples and such to make sure that this really SHOULD work. Only when I tried explicitly casting the anonymous delegate to a Predicate<Whatever> did I get a proper compiler error:
'System.Predicate<Whatever>': not all code paths return a value'

Turns out my actual syntax error was being caught by the compiler and incorrectly reported.

Just a heads-up, in case it happens to anyone else.
Ladybug bug ID is FDBK50271, if anyone cares.

21 Comments

• Thomas Tomiczek said Tuesday, May 23, 2006 10:17:16 AM

  THAT is interesting. I found that behavior occasionally, too, but never managed to track it down to the secondary error that gets supressed. Thanks for that one. I hope MS fixed it soon. That simply is - bad. Gets in your way.

• Jay R. Wren said Thursday, June 1, 2006 3:50:33 AM

  I just ran into this myself and your blog helped. I read the 'not all code paths return a value' and thought to myself DUH!

• Shaun said Friday, September 28, 2007 4:24:53 PM

  That really helped a lot - thanks so much!

• Edvard said Wednesday, November 7, 2007 3:49:59 PM

  Thanks much, this really helped

• Jon said Friday, November 16, 2007 5:20:58 PM

  This helped a LOT. Saved me from a lot of time trying to figure out what the problem was. Thanks!

• Louis said Thursday, March 27, 2008 6:30:50 PM

  Thanks a lot. You saved me precious time.

• ben coates said Wednesday, April 9, 2008 12:14:01 AM

  That's exactly what i had wrong, thanks!

• Anders said Saturday, May 24, 2008 1:53:47 PM

  Thanks. Hope the compiler bug gets fixed soon. In my case I accidentally wrote '=' instead of '=='...

• BCoelho2000 said Monday, October 27, 2008 2:19:27 PM

  This bug made me lost several minutes of my precious time!!!!! I even thought that I didn't know how to use anonymous methods... Thank you!

• ilyas said Thursday, February 5, 2009 8:08:01 PM

  This bug also got me. Thanks for your blog. In my case my anonymous method was returning an int by mistake instead of a bool value.

• Howard said Thursday, August 13, 2009 6:38:53 PM

  You are a godsend today! That was driving me nuts...

• stimul8d said Monday, November 16, 2009 5:11:28 PM

  pretty poor form from the compiler though it should have just been... List list = // get list outputList = list.FindAll(delegate(Whatever item) { return (//blah blah); } );

• Travis Haws said Tuesday, January 26, 2010 10:41:27 PM

  Wow thanks for this.

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